Sawmill hydraulic carriage assembly



Oct. 2, 1951 G. E. zwElFEl. ErAL 2,569,842

SAWMILL HYDRAULIC CARRIAGE ASSEMBLY Filed March 12, 1947 INVENTORS Patented Oct. 2, 1951 SAWMILL` HYDRAULIC CARRIAGE ASSEMBLY George Companillortland, Oreg., a partnership Application March `12, 1947, Serial No. `73(120 2 Clanis, (Cl. 143-108) The .pretentinventien reldteetea .carriage der Sernbly fer ndern .sewrnills .and merenert' nldrlv pertains .te.hydrenlidellvaetnated. anpe .tds .fer ddeirrrnevins leeeereants. inte repeated contant Witnthe .blade df annuler. driven saw, .whereby to Sew them intdbedrds..

t efemmen hrdetee te sawlessinto beards by placing them` on a sawmill carriage, which is reeipreedtedwitn restent. .te .e newerdriven new. de the...eerrieee .is advanced against the n Cut-1S .mede through .the lee to ferm a heard The .direeton .df metten ef Athe 4Carriage .is then reversed, .the .19e shifted e desired ernennt in a lateral Seiidn, .and andthe-r pass .made to .eut Off @neither teerd Bvreneatins this. operation es eftenee is neeeseery, .the 19e may ne .entirely reduced `te .beards ef a predetermined width.

.Befeddse ef the. .er construction .of .a Sew., .the rete at .wlrieh the lee; is rnovedis of eltiee mneridrlee in .determining.tneenieiency ef `the sewing operation ,and the .quality .of o the nrnduetebtened- A eernprises aplurality ef teeth en .e .body .Dertien .eernprising .a blade. er diee.- ,Between n.the .teeth are edvities termed "efillleidf These. serve the illneten of .Carrying nuev theeewdiret edt rrem the 1de .bythe editing peinte .Of .the teeth .The 'Widthef .tneeuttne Pernis. iS eredtel'then `that ef the .bedv nertien f the Serf Order .te .allow .e eleerenee between the .letter end. tnedelid reed en .either .Side- The leedvefthe ,Sew thus .is .enabled .te .more .freely and Witheet bindineer .friction Within the .eut .ferrnedby tneeetien ef `the `teeth .en the 1de.

1t will be .apparent .therefore that if the rate at which a log is driven `against a stationary newer Serv ie te@ elOW, the sew will netenteneneh Weed `tr ..f1.1tne edlletseemnletelv and ,es .a .een- 'eednenee `the Sew will Operate .et Only .leert efliency. AIt will alsoconsurne rnore power by cutting the sawdust too nne. If, on the .other hand, ,the rete is .toe great, more eewdnstie .formed .than .een ne. carried away .in the gnllete The surplus 4sawdust packs and `wedges into the space between the blade 0f the Sew and the Solid 4Weed on either sid `with the result that the saw does not. have free clearance .and friction developsE This causes the blade o f the saw `toheat up, whereupon it loses its tension and waversoso that a true out is not obtained. There is thus a cerf tainV optimum Vsneed at which the log must be advanced against the saw if maximum cutting Aeficiency and optimum performance Yof the `saw are to be obtained.

Uniform `operation .of the carriage at opti,- mum cuttingspeeds is made .diiicult by atleast two factors, i. e. the variable loads placed upon the carriage drive and the lack of sensitivity of the carriage drive mechanisms of the prior art te ,changes ia Control settings. variable loads arelimposed upon the drive because ofthe fact that clohsiderablpowerlmust be applied initially tostart the loaded carriage from itslosition of rest r and advance it toward the saw. Further power application is required at the moment-of lmpactljtween the` saw and the log to overcome shock load. Then, as the saw progresses through the log, it passes'through areas Vof varying re-` sistance. It encounters, `for example, sections `.of 'increased diam't 1'* and obstacles" such .as s tonesQpieces of rnetaland 1argeknct`s,`through which it lcuts slowly. 11n these' situations it is necessary to ue'lerate .or step the motion of the carriage in ordery to avoid damage to the saw. "Thesaw also lencounters cavities, decayed areas and pitchpockets which offer *but` relatively little resistance, when theintion of the carriage may" be accelerated. o Finally,` when the cutis ,c oinplated,` thelcarriage runs free of the Ysaw and tends to'aclzcelerat` suddenly and greatly because of itsvmo'lnentum; "w` r Inaddition; uniform4 operation of the carriage at optimum cutting speeds has been made dini- .eultifnet .mpeeeible .by the feet 'that Prier .nrt driving `iechariisnis,l have not been subject to positive,` precise control.` "Such driving` `rnfechaf nisrns have included electric motors, stearnfenT gings, and pneumatic engines@ The operating speed o f eachof these power sources is an inverse function of the'loadplacedupon it. 'Any fluo;- tualtid inload produces acorre'spondng"change in speed. .Thus when'the load is increased, the speed is .red d. To 'compensate for this itis .Iieee'esri t Create-the newer in erder te .Gerry .the incra'sedl ad.4 Conversely .when the load is decreased; th -speed""t'i'ids tofincre'ase Tand lit is then ynecessary ,Hence ,orderxte more .trie edrrreee etent.- mum rates throughout the entire cut, it nec,- essarr` for .the .Sawyer te .ediimdte :the eeet. 0f changing reads -nnen the speed of .the e rriege- He must gaugethe .amount .by whiehthe .ear- `riage Will llle .deeelerated when thesawgfirst bites :into .the 10g and. how much .it .will be deeelerated and accelerated `.as Ithecsaw meetsareas of` i.n-

' disadvantages also are present.

acces-iai so that optimum speeds are approached as close- ,Y

ly as possible throughout the entire pass. 'Although a sawyer develops great skill in soV doing, the limitations of the driving mechanism are such as to make precise control of the carriage speed a virtual impossibility with the result that the saw is operating at less than its full capacity during certain portion of the cut, and at more. l

than its capacity during others. above, this lowers the quality of the lumber sawed as well as the efficiency, of the sawing operation. It also makes the efcient operation of the'entire mill largely dependent upon the presence on its operating staff of a Sawyer of large experience and great skill.v

Although the inability to control the velocity of the carriage with a sufficient degree of precision constitutes a primary disadvantage of the carriage actuating means of the prior art, other The necessity of using steam power plants, steam lines and steam cylinders in. a steam drive creates a definite nre hazard and is in part responsible for the high fire insurance rates applicable to sawmill coverage. The use of electric motors is disadvantageous since the velocity of operation is Variable stepwise only and they cannot be controlled with the precision required to feed a saw successfully. Furthermore, they are diflicult to reverse, expensive` and usually are dependent upon a source of direct current, which is not available to the average mill.

It is therefore the general object of the present invention to provide an apparatus for moving a log or other large piece of wood against a power driven saw at optimum cutting velocities.

It is a further object to provide a sawmill carriage assembly which will move at a rate which is independent of the load placed upon it. Y Y

It is a further object to provide an apparatus for moving a log against a power driven saw, the direction and speed of motion of which apparatus are subj ect to positive control.

It is a further object to provide a sawmill carriage assembly which will cooperate with a power driven saw in such a manner that eachtooth of the saw will exert maximum and optimum cutting action during the cutting operation.

The manner in which the foregoing and other objects of the invention are accomplished will be apparent from a consideration of the accompanying specification and claims, taken together with the accompanying drawings wherein:

Figure l is a diagrammatic side view of the sawmill carriage assembly of the invention illustrated in the act of moving a log against the cutting edge of a power driven saw;

Figure 2 is an enlarged side view of a portion of a saw such as is illustrated in Figure 1, illustrating the form and manner of arrangement of the teeth; and

Figure 3 is a cross sectional view of a portion of a saw taken along the line 3--3 of Figure 2.

In Figure 1, a'log which is in the process of being sawed into boards is represented by the numeral IIJ. The log is positioned upon the wheeled vehicle Il, commonly termed a log car- As explained riage, which moves on tracks, one of which is indicated at l2. The tracks in turn are mounted on the platform l5. Centrally located with respect to the platform is the saw i6 which, in the form illustrated, is a band saw. This is represented in the act of sawing through the log to form the slab Il.

Actuation of the carriage is obtained through the elongated flexible member, or cable, indicated at 20, 20, 20, attached to the carriage in such a manner that the latter may be reciprocated with respect to the saw. This is accomplished by passing the cable over and around circular members, which preferably are in the form of grooved pulleys, or sheaves in substantial alignment with each other. One sheave 2l is located forwardly of the carriage, While the other sheave, 22, is p0- sitioned toward the rear. The iront sheave may be supported through the axle 25 journalled into the sheave box 26 which is anchored to a beam or other structural member 2`I. The rear sheave 1s supported similarly through the axle 30 extending into the rear sheave box 3l which is attached to the structural member 32. It usually is preferable to have one or both of the sheaves adjustable with respect to the cable so as to make possible taking up slack therein, as by means of a take-up yoke.

To enable moving the cable, and hence of the carriage to which it is attached, the cable is wound around a cylindrical member or drum, indicated at 35. It will be apparent that as the drum rotates in a clockwise direction, the length o r the cable attached to the front end of the carriage will be shortened, thereby drawing the carriage, and the log resting thereon, toward the cutting edge of the saw. Conversely, as the drum 1s rotated in a counterclockwise direction, the carriage will be moved in a direction which is away from the cutting edge of the saw. There thus is provided a means for moving the carriage from a position in front of a saw toward and against the same until the cut is made and then reversing the direction of motion of the carriage until it has returned to its starting position.V By making a series of passes in this manner, the log being shifted in a lateral direction with respect to the saw at each pass, a log resting on the carriage may be reduced to smaller pieces.

The drum 35 is caused to rotate by means of the constant displacement hydraulic motor 36, which operatively is connected to the drum in any suitable manner, as by means of a belt and pulleys, a gear reduction train, or otherwise. Both motor and drum are mounted together on a platform or supporting structure 31 which preferably is positioned directly below the track on which the carriage moves, thereby placing the drum 35 in substantial alignment with the sheaves 2| and 22.

Hydraulic uid is supplied to the motor 3B through the lines indicated at 40. These in turn are attached to the pump 4l which is driven by any suitable source of power, as by the electric motor 42. The pump 4| is of the variable displacement, two-directional type having an overload capacity which is less than that of the electric motor 42. It can supply a variable amount of hydraulic fluid to the hydraulic motor 36, the iluid being delivered through either of the lines 40 at the option of the operator. The quantity of fluid delivered by the pump, and the direction of ow of the iluid is controlled through the single control lever 45, connected to the cables V46 passing over the pulleys 41. The cables 46 preferably are attached to the sawyers lever I8 mounted on the platform in the vicinity of the saw. It affords the only means required by the sawyer for controlling the direction and rate of motion of the carriage.

As a safety measure, it is desirable to include in the control circuit the weighted member 49, attached to the lever 45. This member serves the purpose of automatically returning the lever 45 to a neutral position, and hence of stopping the carriage before damage is done, in the event of failure of the cable 20.

During operation of the apparatus, the electric motor 42 is caused to run at a predetermined speed. Since its overload capacity is greater than that of the pump 4|, this speed remains constant during the entire period of operation of the apparatus regardless of the load placed upon the carriage drive. It drives the rotor of the variable displacement pump likewise at a constant speed. When the rotor is in idling position, no hydraulic fluid is delivered to the hydraulic motor 36, However, when the sawyer desires to move the carriage with respect to the saw, suitable movement of the sawyers lever 40 on the platform will effect a corresponding adjustment of the pump control lever 45 through the cables 46, thereby causing the pump to deliver a variable quantity of fluid through one of the lines 40 to the hydraulic motor 36. This causes the drum 35 to revolve, thereby moving the cable 20 and causing the carriage Il to move.

Since hydraulic fluid is incompressible, pumping a given quantity through the motor causes it to run at a corresponding speed which is independent of the load as long as the motor is operating within its rated capacity. The speed of the motor and of the carriage which it drives, is also steplessly variable and instantly responsive to changes of control. Hence as the log is fed to the saw, the speed of the carriage may be controlled precisely at optimum values throughout the entire pass. When it is necessary to reduce the speed of the carriage, as when the saw is traversing large knots or areas of increased diameter, or when it encounters obstacles such as stones and pieces of metal, the speed may instantly be reduced to any desired extent, or stopped altogether, thereby avoiding damage to the saw. Similarly when the saw is traversing areas of relatively low resistance, the carriage speed readily may be increased to an optimum level. Finally, the carriage speed may be maintained at a high level substantially to the end of the cut, since its motion may be reversed quickly and without danger of the carriage running away from itself as might occur upon release of the load when steam or air engines are used as power sources.

As a result, the carriage may be driven throughout substantially the entire cut at a speed such that the saw is operating at maximum efficiency. At this speed, the teeth, indicated at 50, 50 of Figures 2 and 3, cut just suiiicient wood completely to ll with sawdust the cavities or gullets 5| located therebetween. The sawdust then will be carried free of the log without wedging in the space between the log and the body of the saw, which space is determined by the difference between the width of the tooth, as indicated by the dimension a of Figure 3, and the cross section b of the saw body. Hence, the saw is able to move freely without binding or the development of friction sucient to cause it to lose its tension and Waver, and a straight even cut is obtained.

Having now described our invention in a preferred embodiment, what we claim as new and desire to protect by Letters Patent is:

1. A sawmill carriage assembly which comprises a sawmill carriage adapted to reciprocate with respect to a saw, a rotary, hydraulic motor, means for operatively interconnecting the hydraulic motor and the sawmill carriage, a rotary hydraulic pump, conduit means interconnecting the hydraulic pump and the hydraulic motor, motor means for driving the hydraulic pump, valve means for controlling the volume and direction of flow of hydraulic fluid pumped through the hydraulic motor from the hydraulic pump, and hence for determining the speed and direction of motion of the sawmill carriage, a counterweighted lever arm attached to the valve means, a lever pivotally mounted intermediate its ends adjacent the sawyer and remote from the valve means, and a cable interconnecting the lever and the lever arm of the valve means, the lever acting through the cable being adapted. to displace the valve means from a neutral position against the gravitational force exerted by the counterweight, the counterweight being adapted to return the valve to neutral position in the event of failure of the cable, thereby shutting off the ilow of hydraulic fluid through the hydraulic circuit and arresting the motion of the sawmill carriage.

2. A sawmill carriage assembly which comprises a sawmill carriage adapted to reciprocate with respect to a saw, a rotary hydraulic motor, means for operatively interconnecting the hydraulic motor and the sawmill carriage, a rotary hydraulic pump, conduit means interconnecting the hydraulic pump and the hydraulic motor, motor means for driving the hydraulic pump, valve means for controlling the volume and direction of flow of hydraulic fluid pumped through the hydraulic motor from the hydraulic pump, a lever arm attached to the valve means and associated with tensioning means actuated by movement of the lever arm, a lever pivotally mounted intermediate its ends adjacent the saw and remote from the valve means, and ilexible interconnecting means for interconnecting the lever with the lever arm of the valve means, the lever acting through the flexible interconnecting means being adapted to displace the valve means from a neutral position against the force exerted by the tensioning means, and the tensioning means being adapted to return the valve to its neutral position in the event of failure of the flexible interconnecting means, thereby shutting off the flow of hydraulic iluid through the hydraulic circuit and arresting the motion of the sawmill carriage.

GEORGE E. ZWEIFEL. DONALD H. BOOKHUL'I'Z.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 203,467 Lamb May 7, 1878 334,664 Hinkley Jan. 19, 1886 1,056,032 Kitchen Mar. 18, 1913 1,359,679 Fee Nov. 23, 1920 2,056,896 Douglas Oct. 6, 1936 2,234,009 Robinson Mar. 4, 1941 2,401,680 Eaton June 4, 1946 

